The invention relates to arranging data ciphering in wireless telecommunication systems and particularly in Wireless Local Area Networks WLAN.
Recently various wireless local area networks have become common in addition to Public Land Mobile Networks PLMN. Such wireless local area networks include for example networks based on IEEE802.11 standard. Particular attention has been paid to the safety of IEEE802.11 networks by producing a Wired Equivalent Privacy WEP function. The WEP describes traffic ciphering on layer 2 (MAC) between a terminal and an access point supporting IEEE802.11 standard. The WEP is a symmetrical algorithm, in which the same ciphering key is used for enciphering and deciphering data.
However, a problem in some wireless telecommunication networks, such as IEEE802.11 WLAN networks, is that the ciphering keys used for ciphering traffic must be stored in advance in the terminal and access point. If the network does not have the same key as the terminal, then the data between the network and the terminal cannot be ciphered. To add different ciphering keys is difficult, and a safe data transmission cannot always be offered for terminals moving in different networks.